The present invention is directed to a blade with optimized vibration behavior for turbomachinery components in an axial type of construction. The axial-type construction having moving or guide blades for the low-pressure turbine region of a gas turbine and having solid, thinly-profiled blade bodies which are elongated in the direction of the stacking axis, which is a radial direction.
In the case of solid, thinly-profiled and radially long low-pressure compressor moving blades, such as fan blades, it is known to influence the vibration behavior of the blades in the cascade by a mutual contact. In this respect, see U.S. Pat. No. 4,257,741, whose disclosure is incorporated herein by reference thereto and from which German 29 30 465 claims priority. For this purpose, each of the blade bodies on the pressure side and the suction side has a projection pointing in the circumferential direction with a defined wear-resistant contact surface. Since the blades in the cascade virtually never vibrate synchronously, i.e., uniformly and in phase, they are mutually dampened by impact and frictional actions at the contact surfaces of these projections. The projections are often referred to as xe2x80x9csnubbersxe2x80x9d.
U.S. Pat. No. 4,128,363, whose disclosure is incorporated herein by reference thereto, relates to an arrangement of rib-like flow-guide elements on the surfaces of axial compressor blades. The task of the xe2x80x9cribsxe2x80x9d on the blades is to give the flow, which is, at first, in an axial direction, an additional specific radial component. These blades are intended to be used mainly as radiator fans of a motor vehicle. The fluidic effect, which can be achieved with this design, is an increase in the diameter of the cross-section of the flow emerging from the fan. At any rate, the ribs have an exclusively fluidic function.
In a simple manner from the design point of view, the object of the present invention is to modify and, thus, optimize the vibration behavior of solid, thinly-profiled and elongated blades for turbomachinery components in an axial type of construction, with the blade weight and the flow properties remaining largely unchanged.
This object is achieved in an improvement in a blade with optimum vibration behavior of a turbomachinery component as either a moving or guide blade for the low-pressure turbine region of gas turbines having a solid, thinly-profiled blade body which is elongated in the direction of a stacking axis, which is a radial axis. The improvement is that, at a radial distance from both the radially inner blade body end, which is adjacent the platform, and the radially outer blade body end, which is the shroud band, at least one plate-like rib is disposed in an upright position on a surface of the blade body and is oriented in a neutral manner with regard to the flow, and without a relevant angle of incidence to the local flow path, and is integrally connected to the blade body on one of the suction and pressure sides.
The invention proposes to integrate at least one rib which is neutral with regard to the flow in the profiled blade body. This rib, at first, locally increases the planar moment of inertia of the blade body, as a result of which, in particular, the flexural strength about the radial stacking axis or about axes parallel to the latter is considerably improved. However, the local change has an effect on the vibration behavior of the entire blade, so that the mode of vibration and resonant frequency can be specifically influenced and optimized. The increase in the weight and the increase in the flow resistance are negligible in relation to the disadvantages and risks of a blade vibrating in resonance. Since the ribs according to the invention do not touch the neighboring blades, there is neither friction nor wear, and also no impact effects.
Preferably, the blade profile is arched to a more pronounced extent so that at least one rib is arranged on the concave side of the blade profile and a free edge of this rib runs over most of its length approximately in a rectilinear connection between a leading edge and a trailing edge of the blade profile.
The blades can be a cast or a forged design. The at least one rib corresponds to an integral cast or forged contour produced with the blade body.
Other advantages and features of the invention will be readily apparent from the following description of the preferred embodiments, the drawing and claims.